Agreed. I have seen some really, really rough handling of fish before, and they *usually* go on with no problem. BHC and I were talking about what you see during stocking, and watching trout dumped from a tank to a river that has close to a 20 to 40' difference in temperature would impact them in a big way, but after a bit of time, they adjust and are fine. It does shock them, but they make it. Removing a bit of the mucus coating isn't going to kill them, and as long as you don't squeeze them to death, handling them with a wet hand isn't going to cause a problem.
A 20-40 degree temperature shock would kill trout immediately. Hatchery truck tanks are typically filled with water that is a very trout friendly 52 degrees, same temp as the hatchery raceways. As the season progresses they "temp" the tanks & trout in them up into the 60s to match the average stream temps as best they can. Removing a bit of the mucus coating can kill them because that's basically their immune system and remving a prition of it makes them very susceptible to disease and infection. No they won't die immediately after you released them, it may take a week. Just because a "rough-handled" fish swam away with no apparent problem doesn't mean there won't likely be one soon.